376 PROf'EEDINOS OF THE NATIONAL MUSEUM. vol.52. 



PLECIA EXPLANATA, new species. 



Male. — Length, about 7.3 mm. as preserved, but end of abdomen 

 gone; black or dark browTi, abdomen not banded; wings quite long 

 and narrow, 8 mm. long and 2.9 broad, dusky; anterior femora very 

 robust. Anterior cross-vein shorter than distance from it to fork of 

 fourtli; anal cell narrowly open. Tlie following measurements are 

 in microns: Depth of marginal cell at level of anterior cross-vein, 368; 

 third vein from origin to fork, 2,400; third vein from fork to end 

 (lower branch), 2,320; length of upper branch of third (second vein), 

 800; depth of submarginal cell at level of end of second vein, about 

 288; third vein from origin to anterior cross-vein, 1,330; length of 

 anterior cross-vein, 240; anterior cross-vein to fork of fourth, 320; 

 base of third posterior cell to basal comer of second, 1,200; fourth 

 posterior cell on wing-margin, about 1,440. 



Florissant, in the Miocene shales. A relatively narrow-winged 

 species, readily known from the other Florissant forms by the meas- 

 urements. 



Type.— Cut. No. 62536, U.S.N.M. 



ACREOTRICHITES, new genus (Bombyliidae). 



Small flies allied to Acreotrichus Macquart; body not hairy; thorax 

 robust, elevated in profile; abdomen rather slender; antennae with 

 very long black hair, arranged nearly as in AcreotricJius, the first two 

 joints densely hairy, the third long-pyriform, with a tuft of long hair. 

 Wings with four posterior cells, all wide open; second submarginal 

 very long and narrow, flaring apically; second vein not turned up at 

 end; discal cell small, the anterior cross-vein much before its middle; 

 praefurca short; anal cell very broad, closed a short distance before 

 wing-margin. 



Type of the genus. — AcreotricMtes scopulicornis, new species. 



ACREOTRICHITES SCOPUUCORNIS. new species. 



Plate 31, fig. 6. 



Length, 4.5 mm.; wing, 3 mm.; black, with smoky wings. The 

 follo^ving measurements are in mircons: Praefurca, about 350; 

 length of second submarginal cell on lower side, 1,010; basal comer 

 of second submarginal apicad of vertical level of end of discal cell, 

 112; discal cell on first posterior, 656; discal on first basal, about 

 320; discal on fourth posterior, 480; width of anal cell at level of 

 base of fourth posterior, 320; posterior cells on wing-margin, first 

 and second, each 240, third 480, fourth 832. Vein separating discal 

 cell from third posterior having a double curve (as in Systropus 

 foenoides). 



Florissant, in the Miocene shales. It was preserved on the same 

 piece of shale as Urortalis caudatus, about 25 mm. away from it. 



